For the purpose of transferring pictures, designs or patterns and, in general, any arrangement of elements that make up the structure of a work of art or craft project, it is often desirable to use a stencil, that is to say, a stiff sheet of material into which grooves or elongated openings have been cut to facilitate transfer of the pattern or design to a sheet of paper or cloth. The pattern present in the stencil is duplicated by placing the point of a pencil or pen in one of the slots or openings in the stencil and tracing each successive one to produce a series of lines on the underlying surface corresponding to the original pattern.
Stencils of this kind were originally produced by hand. While suitable stencils could be made, the process was arduous, time consuming and expensive. The operation was normally performed by placing a sheet of stiff plastic, say 15 mils thick, on the surface of a sheet of glass and then manually cutting elongated openings or slots in the sheet to form a picture, design or pattern. In addition to the slowness and high cost of the process, the slots were wider on one side of the sheet than the other because cutting tools cut a tapered opening.
Automated methods have been proposed for producing patterns and designs but these prior methods have not been entirely satisfactory for mass producing stencils at high speed and at a low cost. In the development of the present invention, an attempt was made to cut patterns in sheet material using a high-speed drill or the beam from a laser by individually measuring by hand the relative location and position of each of the lines to be duplicated and feeding the resulting location numbers into an electronic data storage means suitably coupled to a motor for imparting relative movement between a cutter and a blank stencil to trace out each successive line that was placed in storage. This process was laborious, time consuming and expensive. Most of the expense resulted from the fact that the location, position and curavature of each line had to be carefully determined manually by measuring from reference points. The distances had to then be recorded manually.
It later became clear that what was needed was to find a way to automatically plot the coordinates of points located along the lines to be transferred and then automatically retrieve the stored information rapidly in sequence to cut the design or pattern in the stencil sheet. To do this successfully, it is necessary to be able to work effectively with any picture, art object, design or pattern which may include a large number of straight or curved lines in any position or location and of a variety of lengths with a provision for maintaining small connecting ligaments between adjacent line segments where desired to keep the stencil in one piece even though the pattern may include complete circles and other forms that are closed upon themselves. Another requirement is the necessity for being able to successfully reproduce at high speed patterns including a series of lines that may be of various shapes including portions which are straight or almost straight and other portions curved either to the right or left with various curved sections of different radii. It is also necessary to be able to record and store patterns for any length of time including patterns that are both geometric in shape or otherwise as in the case of pictures of living beings such as animals, human beings or plants as well as scenery or the like.